The present invention relates in general to apparatus used in connection with forming cast-in-place caseless concrete piles. More particularly, the present invention relates to the construction of various hopper devices, and the manner of installation and use of the hopper devices, at a pile-forming site, to direct and control the flow of fill material designed to form the caseless concrete pile into the pile-forming cavity being formed in the ground. The hopper devices are used in the course of practice of the method of forming cast-in-place caseless concrete piles by driving into the ground a pile tip or driving foot member releasably assembled onto a hollow tubular driving mandrel to form the pile-forming cavity or hole, and concurrently filling the pile-forming hole with concrete.
One known procedure for forming caseless concrete piles for which the fill hoppers of the present invention are suitable involves advancing into the soil some sort of pile tip, achieved, for example, by the use of a hollow driving mandrel and conventional pile-driving rig, and continuously providing an adequate supply of fluid concrete around and/or within the mandrel so that the concrete can flow or be directed into the ground cavity being formed by the driving tip and mandrel. In practicing this pile-forming procedure, it is desirable to have some type of receptacle or hopper device for containing the concrete prior to its descent into the cavity being formed by the tip and driving mandrel assembly, and for preventing unnecessary spillage. Various embodiments of these devices, frequently called fill hoppers, have been proposed. Some designs for such fill hoppers proposed by others have embodied shapes wherein downwardly converging planes or curvilinear surfaces are formed around the driving mandrel, thereby directing the flow material into the cavity. To the best of applicant's knowledge, it has been customary to merely rest the bottom of these prior art fill hoppers upon the ground at the pile site, and considerable difficulty has been experienced in achieving an effective seal between the bottom of the fill hopper and the soil. The lack of this seal has caused excessive spillage of concrete during driving of the mandrel, and thereby adversely affected the economics of the pile-forming operation. Another problem encountered with these prior art fill hoppers is that their weight and size made them difficult to move about to the many pile-forming sites of a given building excavation or pile-driving job, even when the hoppers are mounted on wheels.
An object of the present invention is the provision of novel apparatus for formation of cast-in-place caseless concrete piles involving forming of pile-forming cavities or holes in the soil, by driving a driving tip or foot member into the soil with a driving mandrel extending vertically downwardly through a lower discharge opening of a fill hopper containing a supply of flowable concrete to be directly supplied to the pile-forming cavity concurrently during its formation, wherein the hopper is provided with a downwardly projecting lower extremity or skirt forming a surround about the lower discharge opening to follow the driving tip or foot into the ground during initial penetration of the soil, and thus provide a seal with the soil at the lower opening of the hopper.
Another object of the present invention is the provision of a novel fill hopper construction for use in forming cast-in-place caseless concrete piles by a driving tip or foot member releasably secured to a driving mandrel extending downwardly through fill hopper, wherein the fill hopper can be readily handled by two men, to be moved about to various pile-forming sites in a given pile-forming job.
Also, in the practice of forming cast-in-place caseless concrete piles by the method hereinabove discussed, it has been found that a problem of drift is encountered from time to time, wherein the center axis of the fill hopper and/or of the driving mandrel moves out of the true vertical or perpendicular position during the course of driving the driving tip into the ground for forming a given pile. This results in pilings which are not vertical and sometimes result in piling being driven in such a way that they intersect each other during the driving. Obviously, the intersection of one pile with another is undesirable from the design standpoint. In addition to this, when piles are formed which utilize a boot-like driving tip, wherein the outside diameter of the mandrel is somewhat smaller than the inside diameter of the sleeve portion of the driving boot, there can be a tendency for the boot to move out of vertical alignment with the mandrel, tending to cause the driving force to be directed at an angle away from the vertical, and thus lead the driving foot and mandrel to an out-of-vertical position. To the best of my knowledge, others have not addressed themselves to these problems.
Another object of the present invention, therefore, is the provision of a fill hopper which has means facilitating precise centering of the driving mandrel with the center axis of the fill hopper and maintenance of the mandrel in a vertically aligned position relative to the vertical axis through the top of the pile-driving site and the vertical center axis of the hopper. This is achieved by providing in the fill hopper, in approximately horizontal alignment with its upper opening, an inner ring smaller than the top opening of the fill hopper and supported by rigid horizontal spider support members. This rigid ring, centered in the precise center of the hopper, has an inner diameter corresponding approximately to the outer diameter of the mandrel, and acts as a guide for the mandrel to keep it in vertical alignment. The sealing skirt surrounding the bottom opening of the hopper may be of proper size to guide the mandrel and/or the boot-type tip, or a plurality of circumferentially spaced radial plates or rails or a lower guide ring supported by spider members, may be provided at the lower extremity of the hopper, providing guide surfaces in a circular path smaller than the diameter of lower hopper discharge openings when the latter are substantially larger than the mandrel to increase concrete flow. These plate edges or lower ring act as a lower bearing or guide for the mandrel, and for the driving tip or foot when it is of boot-like construction, coacting with the upper bearing or guide formed by the upper centering ring, to maintain the hopper axis and mandrel vertical.
Yet another problem encountered in the forming of caseless cast-in-place concrete piles, using the herein discussed method, occurs because of the weight of the concrete, which is present in the hopper during driving. Often this large weight becomes unstable, and moves to one side of the fill hopper, or its center of mass moves away from the geometrical center or vertical center line of the hopper, so that the hopper, because of soft soil conditions, is shifted to an out-of-plumb position. This out-of-plumb condition, in turn, causes the driving mandrel to become canted to one side, or inclined relative to the true vertical axis, and it also goes out of plumb. This has the result of producing piles which are not perpendicular.
Another object of the present invention, therefore, is the provision of a fill hopper, with or without guides for the mandrel and driving tip, which hopper is equipped with three or more hydraulic or mechanical jack mechanisms for leveling the hopper prior to and/or during driving of the mandrel. The jacks may be operated either manually or automatically, and in any event are used to level the hopper and maintain its level plumb condition after driving has commenced.
Another significant problem encountered in the forming of cast-in-place caseless concrete piles using the above-described methods arises in connection with the movement of the fill hopper from the site of one pile to the site of the subsequent pile. This becomes a particularly serious problem when using a hopper which is of a size which is not intended to be completely empty of concrete at the end of the forming of one particular pile. Naturally, the concrete which remains in the fill hopper at the conclusion of forming of one pile makes the hopper so heavy that it cannot be easily moved. Another object of the present invention is the provision of a fill hopper for use in the herein described method of caseless concrete pile formation, wherein the fill hopper is equipped with hooks for attachment thereto of lines or cables from the pile-driving rig, so that the hopper can readily be picked up by the cables of the pile-driving rig and moved to the site of the next pile. By provision of a gate mechanism in the fill hopper which can be closed to prevent flow of concrete from the hopper into the bottom-discharge opening thereof, the hopper gate can be closed to retain the residual concrete in the hopper while it is moved to the new pile site.